Wheels rotate opposite after coupling change

Hello, I changed the clutch in my car and now screwed the wheels back on again. In the still broken condition I noticed that 1. the wheels can be turned despite the inserted first gear and 2. the opposite wheel turns along and in opposite direction. 3. In idle mode they turn in the same direction, but only briefly. I did not adjust anything at the gearbox except that I have closed and connected the switching cables for the gearbox expansion. Do you have any idea what’s going on here? Is this a basic set-up in the gearbox? I have not started the engine again as a precaution. Could this possibly solve the problem? Does anyone know a website where the problem is described and solved? Unfortunately, I have found nothing useful. Thank you for your help!